Method, apparatus and article for microfluidic control via electrowetting, for chemical, biochemical and biological assays and the like

ABSTRACT

An active matrix microfluidic platform employs thin film transistor active (“TFT”) matrix liquid crystal display technology to manipulate small samples of fluid for chemical, biochemical, or biological assays without moving parts, for example, using a two-dimensional matrix array of drive electrodes. The active matrix microfluidic platform may employ existing active matrix addressing schemes and/or commercial “off-the-shelf” animation software to program assay protocols. A feedback subsystem may determine an actual location of a fluid in the microfluidic structure, and provides location information to for display, for example, on an active matrix display, and/or to control movement of one or more fluid bodies in the microfluidic structure.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This disclosure is generally related to the manipulation offluids, for example, manipulating fluids for performing chemical,biochemical, cellular and/or biological assays, and more particularly toelectrowetting to manipulate electrolytic fluids, for example reactantssuch as agents and reagents.

[0003] 2. Description of the Related Art

[0004] Two of the primary factors currently driving the development ofmicrofluidic chips for pharmaceuticals, the applied life sciences, andmedical diagnostics include: (1) the reduction of sample volumes toconserve expensive reagents and reduce disposal problems; and (2) thereduction of test turnaround times to obtain laboratory results. Throughthe engineering of new processes and devices, time-consuming preparatoryprocedures and protocols can be automated and/or eliminated. This hasbeen the motivation behind the development of microfluidics associatedwith lab-on-a-chip systems, biochips, and micro Total Analytical Systems(μTAS). The result has been a large number of mechanical designs forpumps, valves, splitters, mixers, and reactors that have beenmicro-fabricated in channels using photolithographic and other bondingand assembly methods.

[0005] There is also a growing need in the fields of chemistry,biochemistry and biology for performing large scale, combinatorialtesting. One type of large-scale combinatorial testing employsmicroarrays. Each microarray consists of hundreds or thousands of spotsof liquid applied to a slide or “biochip.” Each spot may, for example,contain a particular DNA segment. The microarrays are created usingrobots which move pins to wick up the appropriate fluid from reservoirsand to place each individual spot of fluid precisely on the slide. Thehardware is expensive and the slides are time consuming to manufacture.

BRIEF SUMMARY OF THE INVENTION

[0006] Under one aspect, an active matrix microfluidic platform employsthin film transistor active (“TFT”) matrix liquid crystal displaytechnology to manipulate small samples of fluid for chemical,biochemical, or biological assays without moving parts, for exampleusing a two-dimensional matrix array of drive electrodes.

[0007] In another aspect, the active matrix microfluidic platform mayemploy existing active matrix addressing schemes and/or commercial“off-the-shelf” animation software to program assay protocols.

[0008] In a further aspect, a feedback subsystem determines an actuallocation of a fluid in the microfluidic structure, and provides locationinformation for display, for example on an active matrix display, and/orto control movement of one or more fluid bodies in the microfluidicstructure.

[0009] The active matrix microfluidic platform may provide a low costand efficient method and apparatus for the pharmaceutical industries toperform drug-screening applications. The active matrix microfluidicplatform may also provide a low cost and efficient method and apparatusfor the chemical industries to perform combinatorial chemistryapplications. The active matrix microfluidic platform may additionallyprovide a low cost and efficient method and apparatus for the bioscienceindustries to perform gene expression microarray research. The activematrix microfluidic platform may further provide a low cost andefficient method and apparatus for clinical diagnostic bioassay, as wellas lead to additional “lab-on-a-chip” applications.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] In the drawings, identical reference numbers identify similarelements or acts. The sizes and relative positions of elements in thedrawings are not necessarily drawn to scale. For example, the shapes ofvarious elements and angles are not drawn to scale, and some of theseelements are arbitrarily enlarged and positioned to improve drawinglegibility. Further, the particular shapes of the elements as drawn, arenot intended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

[0011]FIG. 1 is a schematic diagram of a microfluidic control system,including a controller in the form of a computing system, and amicrofluidic platform having a microfluidic structure including atwo-dimensional matrix array of drive electrodes, row and column drivingcircuits and a ground electrode.

[0012]FIG. 2 is a schematic diagram of the computing system andmicrofluidic platform of FIG. 1.

[0013]FIG. 3 is a cross-sectional view of one illustrated embodiment ofa microfluidic structure.

[0014]FIG. 4 is a first alternative illustrated embodiment of themicrofluidic structure, having transistors formed in a plane of thedrive electrodes.

[0015]FIG. 5 is a second alternative illustrated embodiment of themicrofluidic structure, omitting a substrate and ground electrode.

[0016]FIG. 6 is an isometric view of the microfluidic structure,illustrating the two-dimensional matrix array of electrodes, the arrayof transistors electrically coupled to respective ones of theelectrodes, and the gate and source lines for driving the transistors.

[0017]FIG. 7 is an isometric view of the microfluidic structure of FIG.6, having the second plate raised to more fully illustrate the geometryof one of the bodies of fluid received in the cavity or interior of themicrofluidic structure.

[0018] FIGS. 8A-8E are cross-sectional views of successive steps infabricating the microfluidic structure.

[0019]FIG. 9 is a schematic view of the microfluidic system illustratingone exemplary embodiment a feedback subsystem employing a set of visualsensors.

[0020]FIG. 10 is a schematic view of the microfluidic systemillustrating another exemplary embodiment a feedback subsystem employinga set of capacitively or resistively sensitive sensors.

[0021]FIG. 11 is a flow diagram of one exemplary illustrated method ofoperating the microfluidic system, including producing an animationexecutable file using animation software.

[0022]FIG. 12 is a flow diagram of an additional method of operating themicrofluidic system including determining a position of a fluid body viathe position feedback subsystem and displaying the actual positionand/or flow path of the fluid body, and or a desired position and/orflow path of the fluid body.

[0023]FIG. 13 is a flow diagram of a further method of operating themicrofluidic system including employing the position feedback subsystemto adjust the operation of the microfluidic system based on positionfeedback.

[0024]FIG. 14 is a flow diagram of an even further method of operatingthe microfluidic system including converting position feedback from theposition feedback subsystem into an animation of an actual flow path.

[0025]FIG. 15 is a schematic diagram of a screen display on an activematrix display of a set of desired flow paths, actual flow paths,desired positions and actual positions for a two bodies of fluid in themicrofluidic structure.

DETAILED DESCRIPTION OF THE INVENTION

[0026] In the following description, certain specific details are setforth in order to provide a thorough understanding of variousembodiments of the invention. However, one skilled in the art willunderstand that the invention may be practiced without these details. Inother instances, well-known structures associated with matrix arrayssuch as those used in active matrix displays, thin film transistors,voltage sources, controllers such as microprocessors and/or computingsystems, photolithography, micro-fabrication, and animation softwarehave not been shown or described in detail to avoid unnecessarilyobscuring descriptions of the embodiments of the invention.

[0027] Unless the context requires otherwise, throughout thespecification and claims which follow, the word “comprise” andvariations thereof, such as, “comprises” and “comprising” are to beconstrued in an open, inclusive sense, that is as “including, but notlimited to.”

[0028] The headings provided herein are for convenience only and do notinterpret the scope of meaning of the claimed invention.

[0029]FIG. 1 shows a microfluidic system 10 having a microfluidicplatform 11 including a microfluidic structure 12 and a controller suchas a computing system 14 coupled to control the microfluidic structure12. The microfluidic structure 12 includes at least one port 16 a forproviding fluid communication between an exterior 18 and an interior 20of the microfluidic structure 12. The port 16 a permits the additionand/or removal of one or more fluids 22 a, 22 b to the interior 20 ofthe microfluidic structure 12 after manufacture and during use of themicrofluidic structure 12. In some embodiments, the microfluidicstructure 12 includes a separate inflow port 16 a and outflow port 16 b.The microfluidic structure 12 may further include one or more valves 24a, 24 b for controlling the flow of fluids through the respective ports16 a, 16 b.

[0030] The microfluidic structure 12 includes an array of driveelectrodes 26. In one embodiment illustrated in FIG. 1, the array ofdrive electrodes 26 takes the form of a two-dimensional matrix array.The two-dimensional matrix of drive electrodes 26 allows movement of thefluids via electrowetting in any direction on the microfluidic structure12, without dedicated hardware defined flow paths. This providessignificantly increased flexibility in use over microfluidic structures12 having hardware defined flow paths, and may be less costly tomanufacture since it allows the use of well-developed techniques fromthe field of active matrix display fabrication and control. In anotherembodiment, the array of drive electrodes 26 describes specific hardwaredefined flow paths, such that the fluids 22 a, 22 b can only move alongthe prescribed flow paths. As discussed above, microfluidic structures12 employing hardware defined flow paths may not be as advantageous asthose employing two-dimensional matrix arrays of drive electrodes 26 butmay realize other advantages such as maintaining sample purity and/oravoiding sample evaporation.

[0031] The microfluidic structure 12 may also include a row drivingcircuit 28 and a column driving circuit 30 to drive the drive electrodes26. In the embodiment illustrated in FIG. 1, the row and column drivingcircuits 28, 30 are formed “on chip,” as part of the microfluidicstructure 12, while in alternative embodiments the row and columndriving circuits 28, 30 are located off of the chip, for example, as aportion of an off chip controller such as the computing system 14 ordiscrete drive controller (not illustrated).

[0032] In some embodiments, the microfluidic structure 12 may furtherinclude one or more ground electrodes 32, spaced perpendicularly fromthe array of drive electrodes 26. The ground electrode 32 provides aground potential to the body of fluid 22 a, 22 b.

[0033] The microfluidic structure 12 may take advantage ofwell-developed technologies associated with the visual display ofinformation and, in particular, the thin film transistor (“TFT”) activematrix liquid crystal displays (“LCD”) that have come to dominate theflat panel display market. For example, existing electrode (i.e., pixel)addressing schemes, frame times, frame periods, display formats (e.g.,SXGA, UXGA, QSXGA, . . . NTSC, PAL, and SECAM), electrode spacing andsize, use of transparent Indium Tin Oxide (“ITO”) as the groundelectrode 32, the magnitude and alternating sign of the appliedpotentials, and the gap dimension between the electrodes and theorientation layers are all suitable for the microfluidic structure 12.Thus, the invention can take advantage of existing active matrix LCDtechnology including fabrication techniques and animation softwareincluding commercially available video generation or editing software todevelop a microfluidic platform 10 for controlling the motion of fluiddroplets via electrowetting droplet control physics.

[0034] The array of drive electrodes 26 and/or ground electrode 32 isdriven to manipulate samples or bodies of fluid 22 a, 22 b to performchemical, biochemical, or cellular/biological assays. The fluids 22 a,22 b may be in the form of electrolytic drops or droplets ranging insize from picoliters to microliter. The fluid quantities can be divided,combined, and directed to any location on the array 26. The motion ofthe fluid bodies 22 a, 22 b is initiated and controlled byelectrowetting. This phenomenon is a result of the application of anelectric potential between a body of fluid 22 a, 22 b such as a drop ordroplet and a drive electrode 26 that is electrically insulated from thebody of fluid 22 a, 22 b by a thin solid dielectric layer (illustratedin FIGS. 3-7). This locally changes the contact angle between the bodyof fluid 22 a, 22 b and the surface of the dielectric layer, resultingin a preferential application to one side of the fluid body 22 a, 22 bproviding unbalanced forces parallel to the surface. The unbalancedforces result in motion of the fluid body 22 a, 22 b.

[0035] The use of electrodes 26, 32 and thin film technology to utilizeelectrowetting to arbitrarily manipulate bodies of fluid 22 a, 22 b ispotentially revolutionary. The microfluidic structure 12 requires nomoving parts while taking advantage of the most dominant forces thatexist at the small scales: capillary forces. Microfluidic devicesdesigned to utilize a continuous volume of liquid can be disrupted bythe presence of bubbles in microchannels (e.g., use of syringe pumps orother positive displacement pumps). In contrast, the use of interfacialsurface tension is consistent with the typical assay requirement thatdiscrete fluid samples be delivered, mixed, reacted, and detected.

[0036]FIG. 2 is a detailed view of one illustrated embodiment of themicrofluidic system 10.

[0037] The computing system 14 includes a number of subsystems, such asa processor 34, system memory 36, system bus architecture represented byarrows 38 coupling the various subsystems. The system memory 36 mayinclude read only memory (“ROM”) 40, and/or random access memory (“RAM”)42 or other dynamic storage that temporarily stores instructions anddata for execution by the processor 36.

[0038] The computing system 14 typically includes one or morecomputer-readable media drives for reading and/or writing tocomputer-readable media. For example, a hard disk drive 44 for reading ahard disk 46, an optical disk drive 48 for reading optical disks such asCD-ROMs or DVDs 50 and/or a magnetic disk drive 52 for reading magneticdisks such as floppy disks 54.

[0039] The computing system 14 includes a number of user interfacedevices, such as an active matrix display 56, keyboard 58 and mouse 60.A display adapter or video interface 62 may couple the active matrixdisplay 56 to the system bus 38. An interface 64 may couple the keyboard58 and mouse to the system bus 38. The mouse 60 can have one or moreuser selectable buttons for interacting with a graphical user interface(“GUI”) displayed on the screen of the active matrix display 56. Thecomputing system 14 may include additional user interface devices suchas a sound card (not shown) and speakers (not shown).

[0040] The computing system 14 may further include one or morecommunications interfaces. For example, a modem 66 and/or networkinterface 68 for providing bi-directional communications over local areanetworks (“LAN”) 70 and/or wide area networks (WAN) 72, such extranets,intranets, or the Internet, or via any other communications channels.

[0041] The computing system 14 can take any of a variety of forms, suchas a micro-or personal computer, a mini-computer, a workstation, or apalm-top or hand-held computing appliance. The processor 34 can take theform of any suitable microprocessor, for example, a Pentium II, PentiumIV, Pentium IV, AMD Athlon, Power PC 603 or Power PC 604 processor. Thecomputing system 14 is illustrative of the numerous computing systemssuitable for use with the present invention. Other suitableconfigurations of computing systems will be readily apparent to one ofordinary skill in the art. Other configurations can include additionalsubsystems, or fewer subsystems, as is suitable for the particularapplication. For example, a suitable computing system 14 can includemore than one processor 34 (i.e., a multiprocessor system) and/or acache memory. The arrows 38 are illustrative of any interconnectionscheme serving to link the subsystems. Other suitable interconnectionschemes will be readily apparent to one skilled in the art. For example,a local bus could be utilized to connect the processor 34 to the systemmemory 36 and the display adapter 62.

[0042] The system memory 36 of the computing system 14 containsinstructions and data for execution by the processor 34 for implementingthe illustrated embodiments. For example, the system memory 36 includesan operating system (“OS”) 74 to provide instructions and data foroperating the computing systems 14. The OS 74 can take the form ofconventional operating systems, such as WINDOWS 95, WINDOWS 98, WINDOWSNT 4.0 and/or WINDOWS 2000, available from Microsoft Corporation ofRedmond, Wash. The OS 74 can include application programming interfaces(“APIs”) (not shown) for interfacing with the various subsystems andperipheral components of the computing system 14, as is conventional inthe art. For example, the OS 74 can include APIs (not shown) forinterfacing with the active matrix display 56, keyboard 58, windowing,sound, and communications subsystems.

[0043] The system memory 36 of the computing system 14 can also includeadditional communications or networking software (not shown) for wiredand/or wireless communications on networks, such as LAN 70, WAN or theInternet 72. For example, the computing system 14 can include a Webclient or browser 76 for communicating across the World Wide Web portionof the Internet 72 using standard protocol (e.g., Transmission ControlProtocol/Internet Protocol (TCP/IP), User Datagram Protocol (UDP)). Anumber of Web browsers are commercially available, such as NETSCAPENAVIGATOR from America Online, and INTERNET EXPLORER available fromMicrosoft of Redmond, Wash.

[0044] The system memory 36 of the computing system 14 may also includeinstructions and/or data in the form of application programs 78, otherprograms and modules 80 and program data 82 for operation of themicrofluidic platform and providing information therefrom, as discussedin detail below. The instructions may be preloaded in the system memory36, for example in ROM 40, or may be loaded from other computer readablemedia 46, 50, 54 via one of the media drives 44, 48, 52.

[0045] Also as illustrated, the microfluidic platform 10 includes aninterface 84 for providing communications between the computing system14 and the various subsystems of the microfluidic platform such as afeedback subsystem 86, row driver 28 and column driver 30. Themicrofluidic platform also includes one or more voltage sources 88 forproviding a potential to the drive electrodes 26 and/or ground electrode32 in accordance with drive instructions supplied to the row and columndrivers 28, 30 by the computing system 14. While shown as part of themicrofluidic structure 12, in some embodiments the voltage source 88 maybe a discrete component, electrically couplable to the microfluidicplatform 10 and/or microfluidic structure 12.

[0046]FIG. 3 shows a cross-section of a portion of the microfluidicstructure 12 corresponding to a single addressable element (i.e.,pixel).

[0047] The microfluidic structure 12 includes first and secondsubstrates 102,104, spaced apart to form an interior or cavity 106therebetween, and an exterior 108 thereout. The substrates 102, 104 maytake the form of glass plates, and may include a sodium barrier film 110a-110 d, on opposed surfaces of the respective substrates plates. Thesodium barrier film may be applied to the substrate via sintering or viaatmospheric pressure chemical vapor disposition (“APCVD”) for exampleusing a Sierra Therm 5500 series APCVD system.

[0048] A gate insulator 112 may be formed overlying the sodium barrier110 b on the interior surface of the first substrate 102. The array ofdrive electrodes 26 are formed on the gate insulator layer 112. Thedrive electrodes 26 may be transparent, for example being formed oftransparent ITO. An array of transistors 114 (only one illustrated inFIG. 3) may also be formed on the gate insulator layer 112. Thetransistors 114 are electrically coupled to respective ones of the driveelectrodes 26 for controlling the same. The transistors 114 may be thinfilm transistors formed via well-known thin film fabrication processes.A dielectric layer 116 is formed over the drive electrodes 26 and thetransistors 114 to provide appropriate dielectric capacitance betweenthe drive electrodes 26 and the bodies of fluid 22 a, 22 b. Thedielectric layer 116 should be sufficiently thin to provide propercapacitance, yet not have pin holes which could cause electricalshorting.

[0049] One or more ground electrodes 32 may overlay the second glasssubstrate 104, for example, being formed over the sodium barrier film110 d on the interior surface of the second substrate 104. The groundelectrode 32 may be transparent, for example, being formed oftransparent ITO. This allows visual inspection of the microfluidicoperation, which may be advantageously used with at least one embodimentof the feedback subsystem 86, as is discussed in detail below.

[0050] The microfluidic structure 12 may include at least one fluidcompatibility layer 118 forming at least a portion of the cavity 106.The fluid compatibility layer 118 is formed of a fluid compatibilitymaterial, that is a material having appropriate physico-chemicalproperties for the fluid or assay of interest. For example, the selectedfluid compatibility material should have appropriate hydrophobicity orhydrophylicity to prevent the chemical solutions from reacting with thefluid compatibility layer 118. From this perspective, it is unlikelythat the use of polyimide coatings that are used in LCD systems will beuseful for assays of interest. A Teflon or other hydrophobic coatingwill likely be required. The fluid compatibility material may be spacedfrom the electrodes 26, 32 by one or more intervening layers, such asthe fluid compatibility layer 118 a spaced from the drive electrodes 26by the dielectric layer 116. Alternatively, the electrodes 26, 32 may bedirectly coated with the fluid compatibility material, such as the fluidcompatibility layer 118 b directly coating the ground electrode 32 inFIG. 3. In a further alternative, the microfluidic structure 12 may omitthe fluid compatibility layer 118a, where the dielectric layer 116 hassuitable fluid compatibility characteristics, such as hydrophylicity.

[0051] In the manufacture of LCD displays, the TFT/electrode plate andthe ITO/color filter plate are epoxy bonded with spacers. A vacuum isused to fill the gap with the liquid crystal material and an epoxy plugseals the liquid crystal material from the surroundings. As discussedabove, the microfluidic structure 12 includes a number of fluid inletand outlet ports 16 a, 16 b, respectively (FIG. 1), which may beinserted at the edges of the substrates during the bonding step. Anumber of port designs may be used, and may include distinct orintegrally formed values 24 a, 24 b such as a septum, capillary, orother valve to control flow of fluids 22 a, 22 b through the ports 16 a,16 b after completion of the manufacturing process, for example, beforeor during use by the end user. The microfluidic structure 12 may alsocontain an immiscible fluid 121, for example air or some otherimmiscible fluid. The microfluidic structure 12 may also incorporatehumidity control since small bodies of fluids (i.e., droplets) 22 a, 22b will rapidly evaporate if conditions near saturation are not used.Alternatively, or additionally, rather than carefully controllinghumidity, another fluid 121 may be used in lieu of air to preventevaporation.

[0052] Thus, the principle modifications to an LCD design to achieve amicrofluidic structure 12 involves (1) the omission of the liquidcrystal material that normally resides in displays; (2) placement ofappropriate layers to provide dielectric capacitance, chemicalprotection and hydrophobicity for the samples of interest, in lieu ofthe polyimide orientation layers used for displays; (3) placement of aprotective overcoat immediately above the transparent ITO electrode withno other color filters or polarizing films required; and/or (4) theinclusion of one or more ports and/or values to permit placement and orremoval of individual bodies of fluid 22 a, 22 b surrounded by air orother immiscible fluid into the region where the liquid crystal materialnormally resides in displays.

[0053]FIG. 4 shows a first alternative embodiment of the microfluidicstructure 12, where the transistor is formed within the plane of thedrive electrode 26, and the dielectric layer 116 is thinner than thedielectric layer 116 illustrated in FIG. 3. Thus, where the embodimentof FIG. 3 has a different electrowetting force at the transistor 114than at the drive electrode 26 spaced from the transistor 114, theembodiment of FIG. 4 is capable of a more uniform electrowetting force.The thinner dielectric layer 116 provides for a larger change in thecontact angle, allowing easier movement of the bodies of fluid 22 a, 22b. While other permutations are possible, it is desirable to maintain asubstantially flat surface 118 a to avoid adversely impacting fluidmotion.

[0054]FIG. 5 shows a second alternative embodiment, of the microfluidicstructure 12 omitting the ground electrode 32, as well as the secondplate 104 and associated sodium barrier films 110 c, 110 d. Omission ofthe second plate 104, ground electrode 32 and associated barrier films110 c, 110 d allows the microfluidic structure 12 to mate with existingrobotic, ink-jet printer, and DNA micro-array printing technologies.Special attention to avoid rapid evaporation may be required in theembodiment of FIG. 5. The bodies of fluid 22 a, 22 b may be grounded viacontact with a ground line (not shown) carried by the substrate 102, orthe potentials of the bodies of fluid 22 a, 22 b may be allowed tofloat. In such a case, any leakage across the dielectric 116 will beaveraged to ground where the drive voltage alternates polarity.

[0055]FIGS. 6 and 7 show the arrangement of drive electrodes 26 and TFTtransistors 114 in the microfluidic structure 12, as well as, a numberof gate lines 119 a and source lines 119 b (i.e., rows and columnslines) coupled to the gates and sources (not illustrated in FIGS. 6 and7) of respective ones of the transistors 114. The fluid compatibilitylayer 118 a has been omitted from FIGS. 5 and 6 for clarity ofillustration. FIG. 7 also illustrates the geometry of a fluid body 22received in the cavity between the fluid compatibility layers 118 a, 118b overlying the substrates 102,104, respectively. The fluid bodies 22 a,22 b may be moved along a flow path by varying the respective potentialapplied to different portions of the dielectric layer 116 overlyingrespective ones of the drive electrodes 26.

[0056] FIGS. 8A-8E illustrate an exemplary method of fabricating themicrofluidic structure 12 of FIGS. 3-5, in sequential fashion. In theinterest of brevity, a number of intervening depositioning. masking andetching steps to form the various layers and specific structures are notillustrated, but would be readily apparent to those skilled in the artof silicon chip fabrication and particularly the art of TFT fabrication.

[0057] In particular, FIG. 8A shows a gate metal layer 120 on the glasssubstrate 102, after depositioning, masking and etching to form the gateof the transistor 114. The sodium barrier layer 110 b is omitted fromthe illustration for clarity. FIG. 8B shows the deposition of the gateinsulator layer 112, an amorphous silicon layer 122 and a positivelydoped amorphous silicon layer 124. FIG. 8C shows the deposition of thesource/drain metal layer 126 for forming the source 126 a and drain 126b of the transistor 114, and a trench 128 etched in the source/drainmetal layer 122 and the doped amorphous silicon layer 124 over the gatemetal layer 120 to form the gate 130. FIG. 8D shows the formation of thedrive electrodes 26 which typically includes at least depositioning,masking and etching steps. FIG. 8E shows the formation of the dielectriclayer 116 overlying the drive electrode array 26 and transistor array114 and fluid compatible layer 118 a overlying the dielectric layer 116.

[0058]FIG. 9 illustrates a first embodiment of the feedback subsystem86, employing a set of visual feedback sensors, for example, in the formof CCD sensor array or camera 132. The visual feedback sensors may takeany of a variety of forms of photosensitive devices, including but notlimited to one and two dimensional arrays of photosensitive sensors suchas charge coupled devices (“CCDs”), Vidicon, Plumbicon, as well as,being configured to capture either still image or video image data.

[0059] The CCD sensor array or camera 132 is oriented to visual captureimages of the through the transparent electrode 32. The image data 134is supplied to the computing system 14 for analysis and/or display. Theimage date may be in suitable form for display on the active matrixdisplay 56 without further processing. Thus, a live, or delayed, displayof the actual movement of the bodies of fluid 22 a, 22 b may beprovided. Suitable image processing software (e.g., application programs78) may be loaded in the system memory 36 of the computing system 14 toprocess the image data (e.g., program data 86), and to identify aposition of each body of fluid 22 a, 22 b in the microfluidic structure12 at a series of time intervals. The position information may beprocessed to provide an animated display of the bodies of fluid 22 a, 22b, and/or control the drive electrodes 26 of the microfluidic structure12 via drive signals 136 as discussed more fully below.

[0060]FIG. 10 illustrates a second embodiment of a feedback subsystem86, employing a set of position detection sensors 138, and row andcolumn detection circuitry 140,142, respectively. The position detectionsensors 138 may be pressure sensitive, resistivity sensitive, orcapacitivity sensitive.

[0061] One method of detecting the position of bodies of fluid 22 a, 22b (e.g., drops or droplets) involves measuring the resistance betweenadjacent sensor electrodes. If the sensor electrodes are in electricalcontact with the fluid body 22 a, 22 b, the application of a voltagepulse to one sensor electrode can be detected by an adjacent sensorelectrode if the body of fluid 22 a, 22 b is in contact with both sensorelectrodes. If the body of fluid 22 a, 22 b is not in contact with bothsensor electrodes, the resistance of the air/immiscible fluid betweenthe electrodes I too great for a pulse to be detected.

[0062] The feedback subsystem 86 may employ a TFT array of sensorelectrodes by activating a row of sensor electrodes 140 and then pulsingthe potential of one column of sensor electrodes 142 at a time, whilemeasuring the potential at the adjacent sensor electrodes. By rasterscanning through all rows and columns, data representing the location ofbodies of fluid 22 a, 22 b can be provided to the active matrix display56 to visually indicate the current location of the bodies of fluid 22a, 22 b and/or to provide a feedback signal to control the driveelectrodes 26 to adjust the motion of the bodies of fluid 22 a, 22 b.More generally, for any sensor system, the row and column detectioncircuitry 140, 142 receive electrical signals from the positiondetection sensors 138 and provide position information 144 to thecomputing system 14, identifying the position of one or more bodies offluid 22 a, 22 b in the microfluidic structure 12. Suitable row andcolumn detection circuitry 140, 142 is disclosed in U.S. Pat. No.5,194,862 issued Mar. 16, 1993 to Edwards. Suitable processing software(e.g. application programs 78) may be loaded into the system memory 36of the computing system 14 to provide an animated display of the bodiesof fluid 22 a, 22 b, and/or control the drive electrodes 26 of themicrofluidic structure 12 via drive signals 136 as discussed more fullybelow.

[0063] As an open platform, the microfluidic system 10 allowsreconfiguration of protocols through the use of software to specify thepotential of each electrode 26, 32, and thereby control the motion ofindividual bodies of fluid 22 a, 22 b. A protocol for a particular assaymay be controlled by using commercial, off-the-shelf software, forexample video editing software, to create an “animation” to charge theelectrodes 26, 30 adjacent to a droplet edge sequentially so that motionoccurs. Fluid bodies 22 a, 22 b with a lateral dimension (i.e., adimension in the plane of the liquid/solid interface) allowing coverageof some portion of the dielectric layer 116 overlying at least two driveelectrodes 26 can be moved by (1) addressing the electrodes with 8-bitcontrol on the electrode potential that already exists in flat paneldisplays to provide 256 gray levels of light intensity and (2)addressing the display electrodes with control over the 3 displaycolumns associated with Red, Green, and Blue for a display pixel so thatmicrofluidic control can be provided with a factor of 3 increase overthe display pixel density. (E.g., 1280×1024×3 for SXGA format).

[0064] The microfluidic structure 12 may employ TFT AMLCD technologyand/or electrode addressing, and may thus use commercially availableanimation software (e.g., application programs 78). The use of an arrayof many drive electrodes 26 to control drops larger in diameter than oneor two drive electrodes 26 has not been previously reported, while themicrofluidic structure 12 may utilize multiple drive electrodes 26 tomanipulate larger drops, for example causing a large drop to divide intotwo or more smaller drops. In particular, a ratio of at least two driveelectrodes to an area covered by a fluid body 22 a, 22 b (i.e.,electrowetted area) allows the splitting of the fluid body 22 a, 22 binto two fluid bodies. A ratio of at least three drive electrodes 26 toan area covered by a fluid body 22 a, 22 b allows particularly effectivefine grain control of the fluid body 22 a, 22 b.

[0065] While commercial animation software may be used to generateprotocols, this may in some cases require trial-and-error programs toensure robust droplet control, especially for some droplet-splittingprocesses where surface tension forces marginally vary around thedroplet edge. As discussed above, the feedback subsystem 86 may beintegrated to detect the location of droplets, and to ensure robustdroplet control, for example, via closed-loop feedback control. Thiswill prove beneficial for users with samples having varying physicalproperties because a single control algorithm will not be appropriatefor every sample. Customized software for generating animations withinclosed-loop feedback (i.e., real time control) to verify and directdroplet location may prove a major feature of the microfluidic system 10platform as the system gains wide acceptance.

[0066]FIG. 11 shows a method 200 of operating the microfluidic system12. In act 202, an end user produces an executable animation file usingthe user interface of an animation software program or package. In someembodiments, the animation software may be standard, unmodifiedcommercially available animation software suitable for producinganimations or videos for display on active matrix displays. Theanimation software may stored on any computer-readable media 46, 50, 54(FIG. 2) and may be executed on the computing system 14 (FIG. 1), or onsome other computing system (not shown).

[0067] In act 204, the computing system 14 executes the animation file.In response, the computing system 14 provides drive signals to thetransistors 114 (FIG. 3) by way of the row and column drivers 28, 30(FIG. 1) in act 206. In act 208, the transistors 114 selectively couplethe drive electrodes 26 to one or more voltage sources 88. In response,a respective potential is successively applied to respective portions ofthe dielectric layer 116, causing the fluid body 22 a, 22 b to move fromdrive electrode 26 to drive electrode 26, in act 210.

[0068]FIG. 12 shows an additional method 230 of operating themicrofluidic system 12. In act 232, the position feedback sensors sensethe actual position of one or more bodies of fluid 22 a, 22 b. In act234, the position feedback sensor produces position feedback signals. Inact 236, the computing system 14 receives the position feedback signals.In act 238, the processing unit 34 of the computing system 14 providesposition feedback signals to the active matrix display 56. In someembodiments, the position feedback signals require no modification orpreprocessing to drive the active matrix display 56, for example, wherethe position feedback signals are provided by an active matrix ofposition detection sensors 138. In other embodiments, the positionfeedback signals may require preprocessing, for example, where thefeedback signals a provided by an array of image sensors such as acamera 132. Act 240 can be performed in concert with act 242 to displaythe actual and desired locations and/or flow paths at the same time.

[0069] In act 240 the active matrix display 56 displays the actualposition and/or flow path of one or more of the fluid bodies 22 a, 22 b.In act 242, the processing unit 34 of the computing system 14 drives theactive matrix display 56 using the executable animation file to displaya desired position and/or desired flow path of one or more bodies offluid 22 a, 22 b. In some embodiments, the executable animation filerequires no modification or preprocessing to drive the active matrixdisplay 56, for example, where the executable animation file wasgenerated with standard animation software.

[0070]FIG. 13 shows a further method 250 of operating the microfluidicsystem 12. In particular, the microfluidic system 10 employs theposition feedback subsystem 86 to adjust the operation of themicrofluidic system 10 based on position feedback. For example, in act252, the computing system 14 determines a difference between an actualposition and a desired position. In step 254 the computing system 14adjusts a next set of drive signals based on the determined difference.For example, the computing system 14 may delay some signals, or changethe frequency of electrode 26, 32 operation along one or more flowpaths. In act 256, the computing system 14 provides the adjusted nextset of drive signal to the transistors 114 to drive the drive electrodes26, adjusting the movement of one or more of the bodies of fluid 22 a,22 b from a previously defined flow path. Thus, the computing system 14may compensate for inconsistencies in the physical structure of themicrofluidic structure 12 (e.g., differences in drive electrodes 26,transistors 114, and/or across the fluid compatibility layer 118),and/or different properties of the fluid bodies 22 a, 22 b, and/or anyother unexpected or difficult to estimate operating parameters.

[0071]FIG. 14 shows a further method 260 of operating the microfluidicsystem 12. In act 262, the computing system 14 converts the receivedposition feedback signals into an executable animation file. In step264, the processing unit 34 drives the active matrix display 56according to the converted executable animation file to display ananimation of the actual flow path of one or more of the bodies of fluid22 a, 22 b.

[0072] The above-described methods can be used with each other, and theorder of acts may be changed as would be apparent to one of skill in theart. For example, the method 260 can generate an animation of the actualflow path to be displayed in act 240 of method 230. Also for example,the method 250 can be combined with method 260 to display an adjustedposition and/or flow path before providing the adjusted next set ofdrive signal to the transistors 114. The described methods can omit someacts, can add other acts, and can execute the acts in a different orderthan that illustrated, to achieve the advantages of the invention.

[0073]FIG. 15 shows a display 270 on a screen of the active matrixdisplay 56 (FIGS. 1 and 2) of a set of desired flow paths 272, 274,actual flow paths 276, 278, desired positions D₁, D₂ and actualpositions A₁, A₂ for a two bodies of fluid 22 a, 22 b, respectively, inthe microfluidic structure 12 in accordance with the methods discussedabove. In particular, the body of fluid 22 a enters via a first port 16a, and is directed along a desired flow path 272 to an exit port 16 b.As illustrated by the actual flow path 276, the body of fluid 22 a hasdeviated from the desired flow path 272 for any of a variety of reasons,and is at the actual position A1 instead of the desired position D₁ at agiven time. The second fluid body 22 b enters via a port 16 c and isdirected along a desired flow path 274, in order to combine with thefirst fluid body 22 a at a point 280 . As illustrated by the actual flowpath 278, the second fluid body 22 b is following the desired flow path274 as directed and the actual position A₂ corresponds with the desiredposition D₂. The computing system 14 can make appropriate adjustment inthe drive signals to adjust the speed and/or direction of the firstand/or second fluid bodies 22 a, 22 b to assure that the first andsecond fluid bodies 22 a, 22 b combine at the point 280, which may, ormay not have an additional reactant or other molecular components.

[0074] Much of the detailed description provided herein is disclosed inthe provisional patent application; most additional material will berecognized by those skilled in the relevant art as being inherent in thedetailed description provided in such provisional patent application orwell known to those skilled in the relevant art based on the detaileddescription provided in the provisional patent application. Thoseskilled in the relevant art can readily create source based on thedetailed description provided herein.

[0075] Although specific embodiments of and examples for themicrofluidic system and method of the invention are described herein forillustrative purposes, various equivalent modifications can be madewithout departing from the spirit and scope of the invention, as will berecognized by those skilled in the relevant art. The invention mayutilize thin film transistor active matrix liquid crystal displaytechnology to manipulate small samples of fluid for chemical,biochemical, or biological assays with no moving parts. The platformutilizes existing active matrix addressing schemes andcommercial-off-the-shelf animation software such as video editingsoftware to program assay protocols. The teachings provided herein ofthe invention can be applied to other microfluidic platforms, notnecessarily the exemplary active matrix microfluidic platform generallydescribed above. The various embodiments described above can be combinedto provide further embodiments.

[0076] Other teachings on electrowetting include G. Beni and M. A.Tenan, “Dynamics of Electrowetting Displays,” J. Appl. Phys., vol. 52,pp. 6011-6015 (1981); V. G. Chigrinov, Liquid Crystal Devices, Physicsand Applications, Artech House, 1999; E. Lueder, Liquid CrystalDisplays, Addressing Schemes and Electro-Optical Effects, John Wiley &Sons, 2001; M. G. Pollack, R B Fair, and A. Shenderov,“Electrowetting-based actuation of liquid droplets for microfluidicapplications,” Appl. Phys. Left., vol. 77, number 11, pp. 1725-1726(2000); and P. Yeh and C. Gu, Optics of Liquid Crystal Displays, JohnWiley & Sons, 1999.

[0077] All of the above U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet, including butnot limited to U.S. No. 60/333,621, filed Nov. 26, 2001, areincorporated herein by reference in their entirety.

[0078] Various changes can be made to the invention in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the invention to thespecific embodiments disclosed in the specification and the claims, butshould be construed to include all microfluidic platforms that operatein accordance with the claims. Accordingly, the invention is not limitedby the disclosure, but instead its scope is to be determined entirely bythe following claims.

1. A microfluidic structure to move at least one fluid body, comprising:a first plate having a dielectric overlying at least a portion of thefirst plate; a second plate spaced from the first plate to form at leastone cavity between the second plate and the dielectric overlying atleast the portion of the first plate; at least a first port providingfluid communication between the cavity and an exterior of themicrofluidic structure; an array of drive electrodes received betweenthe first and the second plates; and an array of thin film transistors,the thin film transistors coupled to respective ones of the driveelectrodes in the array of drive electrodes to control a respectivepotential applied to respective portions of the dielectric that overlierespective ones of the drive electrodes to move the at least one fluidbody from drive electrode to drive electrode.
 2. The microfluidicstructure of claim 1 wherein the array of drive electrodes is atwo-dimensional matrix.
 3. The microfluidic structure of claim 1 whereinthe first plate and the second plate are substantially planar andparallel to one another.
 4. The microfluidic structure of claim 1,further comprising: a valve coupled to the first port where the valve isselectively actuatable to control a flow of the at least one fluid bodythrough the first port.
 5. The microfluidic structure of claim 1 whereineach of the drive electrodes have a dimension less than a lateraldimension of the at least one fluid body.
 6. The microfluidic structureof claim 1, further comprising: at least one ground electrode receivedbetween the first and the second plates, the at least one groundelectrode spaced relatively from the array of drive electrodes in adirection generally perpendicular to the array of drive electrodes. 7.The microfluidic structure of claim 1 wherein the array of driveelectrodes is a generally planar two-dimensional matrix, wheresuccessive drive electrodes in the array are activated to apply adifferent respective potential to the respective portions of thedielectric in the plane of travel of the at least one fluid body.
 8. Themicrofluidic structure of claim 1, further comprising: at least onehydrophobic layer overlying at least a portion of the dielectric layer.9. The microfluidic structure of claim 1, further comprising: at leastone electrical connector to electrically couple the drive electrodes ofthe array of drive electrodes to at least one voltage source via thearray of thin film transistors.
 10. The microfluidic structure of claim1 wherein the first port provides fluid communication between the cavityand the exterior of the microfluidic structure after completion ofmanufacturing of the microfluidic structure.
 11. A microfluidic system,comprising: at least one voltage source for supplying at least onevoltage; a microfluidic structure comprising a first plate; a secondplate, spaced from the first plate to form at least one cavitytherebetween; at least a first port providing fluid communicationbetween the cavity and an exterior of the microfluidic structure; anarray of drive electrodes received between the first and the secondplates; a dielectric overlying at least a portion of the array of driveelectrodes; and an array of thin film transistors, the thin filmtransistors coupled to respective ones of the drive electrodes in thearray of drive electrodes to control a respective potential applied torespective portions of the dielectric overlying the drive electrodes tomove at least one fluid with respect to the drive electrodes; acontroller programmable to execute a set of driver instructions andcoupled to control the thin film transistors of the array of thin filmtransistors according to a set of driver instructions to supply the atleast one voltage from the voltage source to the drive electrodes viathe thin film transistors.
 12. The microfluidic system of claim 11,further comprising: a computing system; and a computer-readable mediumhaving a set of computer animation instructions for causing thecomputing system to create the set of driver instructions in response touser input.
 13. The microfluidic system of claim 11, further comprising:a computing system; and a computer-readable medium having a set ofcomputer animation instructions for causing the computing system tocreate the set of driver instructions in response to user input, wherethe computer animations instructions comprise a standard, unmodifiedcommercial animation software package.
 14. A microfluidic platform formoving microfluidic bodies having a defined minimum lateral dimension,comprising: a plurality of drive electrodes having a dimension less thanthe defined minimum lateral dimension of the microfluidic bodies; adielectric layer overlying at least a portion of the plurality ofelectrodes; a plurality of thin film transistors coupled to the driveelectrodes to control a respective potential to respective portions ofthe dielectric layer to move the fluidic bodies from a portion of thedielectric layer overlying one drive electrode to a portion of thedielectric layer overlying another drive electrode; and a port providingfluid communications between an interior and an exterior of themicrofluidic platform when the microfluidic platform is in use.
 15. Themicrofluidic platform of claim 14 wherein the dimension of theelectrodes is less than approximately half of the minimum lateraldimension of the microfluidic bodies.
 16. The microfluidic platform ofclaim 14 wherein the dimension of the electrodes is less thanapproximately one third of the minimum lateral dimension of themicrofluidic bodies.
 17. The microfluidic platform of claim 14 whereinthere are at least three drive electrodes in an area equivalent to anarea that would be electrowetted by the fluid.
 18. The microfluidicplatform of claim 14, further comprising: a valve for selectivelyclosing and opening the port when the microfluidic platform is in use.19. A microfluidic platform for moving microfluidic bodies, comprising:a two-dimensional matrix array of drive electrodes, the drive electrodesbeing dimensioned and spaced from one another in the two-dimensionalmatrix such that there is at least three electrodes in an areacorresponding to a surface electrowetted by the microfluidic bodies; adielectric overlying at least a portion of the two-dimensional matrixarray of drive electrodes; a plurality of thin film transistors coupledto the drive electrodes to control a potential applied to respectiveportions of the dielectric overlying the respective drive electrodes tomove the microfluidic bodies between successive portions of thedielectric layer; and a port providing fluid communications between aninterior and an exterior of the microfluidic platform when themicrofluidic platform is in use.
 20. A microfluidic system, comprising:a microfluidic structure having a number of drive electrodes; acontroller coupled to control of the microfluidic structure; and afeedback subsystem having a number of feedback sensors for detecting aposition of at least one fluidic body, if any, in the microfluidicstructure and at least one output for providing feedback positionsignals corresponding to the detected position.
 21. The microfluidicsystem of claim 20, further comprising: a display coupled to receive thefeedback position signals from the feedback subsystem and configured todisplay an image corresponding to the detected position of the at leastone fluidic body, if any, in the microfluidic structure.
 22. Themicrofluidic system of claim 20 wherein the microfluidic structure,comprises: a first plate; a second plate, spaced from the first plate toform at least one cavity therebetween; a two-dimensional matrix arrayformed by the drive electrodes received between the first and the secondplates, the drive electrodes being separately addressable; a dielectriclayer overlying at least a portion of the two-dimensional matrix arrayformed by the drive electrodes; and an array of thin film transistors,the thin film transistors coupled to respective ones of the driveelectrodes to control a respective potential-applied by the driveelectrode to a portion of the dielectric layer overlying the driveelectrode to move the fluid body.
 23. The microfluidic system of claim20 wherein the feedback sensors are capacitively sensitive switches. 24.The microfluidic system of claim 20 wherein the feedback sensors arephotosensitive elements of an imager.
 25. The microfluidic system ofclaim 20 wherein the feedback sensors are resistive sensitive switchingelements.
 26. The microfluidic system of claim 20 wherein the feedbacksensors are pressure sensitive switching elements.
 27. A microfluidicsystem, comprising: a microfluidic structure having a number of driveelectrodes; a feedback subsystem having a number of feedback sensors fordetecting a position of at least one fluidic body, if any, in themicrofluidic structure and at least one output for providing feedbackposition signals; and a controller to produce drive signals and coupledto control of the drive electrodes of the microfluidic structure via thedrive signals, and to receive the feedback position signals from thefeedback subsystem.
 28. The microfluidic system of claim 27 wherein thecontroller is configured to modify the drive signals based on thefeedback signals.
 29. The microfluidic system of claim 27 wherein thecontroller is configured to modify the drive signals based on thefeedback signals, by: determining a difference between the determinedposition of the at least one fluidic body and a desired position of theat least one fluidic body; and adjusting the control of the driveelectrodes based on the determined difference between the determinedposition of the at least one fluidic body and a desired position of theat least one fluidic body.
 30. The microfluidic system of claim 27wherein the feedback sensors are capacitively sensitive switches. 31.The microfluidic system of claim 27 wherein the feedback sensors arephotosensitive elements of an imager.
 32. The microfluidic system ofclaim 27 wherein the feedback sensors are resistive sensitive switchingelements.
 33. The microfluidic system of claim 27 wherein the feedbacksensors are pressure sensitive switching elements.
 34. A method ofcontrolling a microfluidic structure having at least one cavity, atwo-dimensional matrix array of drive electrodes; a dielectric overlyingat least a portion of the two-dimensional matrix array of driveelectrodes; and an array of thin film transistors electrically coupledto the drive electrodes, the method comprising: introducing at least onefluid into the cavity of the microfluidic structure; executing a set ofexecutable instructions to produce a set of drive signals for each driveelectrode in the two-dimensional matrix array of drive electrodesincluding drive electrodes in a desired flow path of the fluid and driveelectrodes out of the desired flow path of the fluid; applying the setof drive signals to the thin film transistors of the array of thin filmtransistors; applying a potential to the drive electrodes in response tothe set of drive signals applied to the thin film transistors; andapplying a respective potential to respective portions of the dielectricoverlying respective ones of the drive electrodes to move the at leastone fluid from at least one drive electrode to at least another driveelectrode, along the desired flow path.
 35. The method of claim 34wherein applying the set of drive signals to the thin film transistorsof the array of thin film transistors includes applying two differentpotential to successive portions of the dielectric in a direction planarwith the desired flow path of the fluid.
 36. The method of claim 34,further comprising: evacuating the fluid from the cavity of themicrofluidic structure after the applying the respective potential tothe respective portions of the dielectric.
 37. A method of controlling amicrofluidic structure having at least one cavity, an array of driveelectrodes and an array of thin film transistors coupled to the driveelectrodes to selectively apply voltage across at least one fluid, themethod comprising: creating a set of executable instructionscorresponding to an animated sequence using a standard, unmodified,animation software package; introducing the at least one fluid into thecavity of the microfluidic structure; executing the set of executableinstructions to produce a set of drive signals; applying the drivesignals to the thin film transistors; and selectively applying apotential to the drive electrodes via the thin film transistors to movethe fluid from at least one of the drive electrodes to another one ofthe drive electrodes.
 38. The method of claim 37 wherein creating a setof executable instructions corresponding to an animated sequence using astandard, unmodified, animation package includes selecting animationcommands from a graphical user interface of the standard, unmodified,animation software package.
 39. The method of claim 37 wherein the arrayof drive electrodes is a two-dimensional matrix array and creating a setof executable instructions corresponding to an animated sequence using astandard, unmodified, animation package includes: manually selectinganimation commands from a graphical user interface of the standard,unmodified, animation software package; and automatically producing arespective drive signal for each of the drive electrodes in thetwo-dimensional matrix array of drive electrodes once each frame period.40. The method of claim 37, further comprising: providing the drivesignals to an active matrix display to display the animated sequence onthe active matrix display before the applying the drive signals to thethin film transistors of the microfluidic structure.
 41. The method ofclaim 37, further comprising: providing the drive signals in unalteredform to an active matrix display to display the animated sequence on theactive matrix display before the applying the drive signals to the thinfilm transistors of the microfluidic structure.
 42. The method of claim37, further comprising: providing the drive signals to an active matrixdisplay to display the animated sequence on an active matrix display atapproximately the same time as the applying the drive signals to thethin film transistors of the microfluidic structure.
 43. The method ofclaim 37, further comprising: providing the drive signals in unalteredform to an active matrix display to display the animated sequence on anactive matrix display at approximately the same time as the applying thedrive signals to the thin film transistors of the microfluidicstructure.
 44. A method of forming a microfluidic structure, the methodcomprising: providing a first plate; providing a second plate; spacingthe second plate from the first plate to create at least one cavitytherebetween; forming at an array of drive electrodes and an array ofthin film transistors overlying at least a portion of the first plate,the thin film transistors electrically coupled to control the driveelectrodes; and providing a port between an exterior of the microfluidicstructure and the cavity.
 45. The method of claim 44, furthercomprising: providing a valve for controlling a flow of fluid throughthe port when the microfluidic structure is in use.
 46. The method ofclaim 44, further comprising: forming a first fluid compatibilitycoating overlying the array of drive electrodes.
 47. The method of claim44, further comprising: forming a first hydrophobic coating overlyingthe array of drive electrodes, the first hydrophobic coating forming atleast a portion of at least one surface of the cavity; and forming asecond hydrophobic coating overlying the second plate, the secondhydrophobic coating forming at least a portion of at least one surfaceof the cavity.
 48. The method of claim 44 wherein forming at an array ofdrive electrodes and an array of thin film transistors overlying atleast a portion of the first plate, the thin film transistorselectrically coupled to control the drive electrodes includes forming atwo-dimensional matrix array of electrodes and a two-dimensional matrixarray of thin film transistors electrically coupled to respective onesof the drive electrodes.
 49. A computer readable medium containinginstructions for causing computer to move fluids in a microfluidicstructure having a two-dimensional matrix array of drive electrodes; adielectric overlying at least a portion of the two-dimensional matrixarray of drive electrodes; and an array of thin film transistors coupledto the drive electrodes, by: producing a set of drive signals for eachdrive electrode in the two-dimensional matrix array of drive electrodes,including drive electrodes in a desired flow path of at least one fluidand drive electrodes out of the desired flow path of the at least onefluid; applying the set of drive signals to the thin film transistors ofthe array of thin film transistors; applying a potential to the driveelectrodes in response to the set of drive signals applied to the thinfilm transistors; and applying a respective potential to respectiveportions of the dielectric overlying respective ones of the driveelectrodes to move the at least one fluid from at least one driveelectrode to at least another drive electrode, along the desired flowpath.
 50. A method of operating a microfluidic system having acontroller, a number of position feedback sensors, and a microfluidicstructure including an array of selectively addressable driveelectrodes, the method comprising: providing drive signals to driveselected ones of the drive electrodes; receiving position feedbacksignals from the position feedback sensors, the position feedbacksignals representing an actual position of at least one fluid body withrespect to the drive electrodes; and displaying a representation of theactual position of the at least one fluid body on an active matrixdisplay in response to the position feedback signals.
 51. The method ofclaim 50 wherein receiving position feedback signals from the positionfeedback sensors, the position feedback signals representing an actualposition of at least one fluid body with respect to the drive electrodesincludes receiving signals from an array of capacitive sensitivesensors.
 52. The method of claim 50 wherein receiving position feedbacksignals from the position feedback sensors, the position feedbacksignals representing an actual position of at least one fluid body withrespect to the drive electrodes includes receiving signals from an arrayof imager sensors.
 53. The method of claim 50, further comprising:displaying a representation of a desired position of the at least onefluid body on the active matrix display.
 54. The method of claim 50,further comprising: displaying a representation of at least one desiredflow path of the at least one fluid body on the active matrix display.55. A method of operating a microfluidic system having a controller, anumber of position feedback sensors, and a microfluidic structureincluding an array of selectively addressable drive electrodes, themethod comprising: providing drive signals to drive selected ones of thedrive electrodes; receiving position feedback signals from the positionfeedback sensors, the position feedback signals representing an actualposition of at least one fluid body with respect to the driveelectrodes; and providing further drive signals based at least in parton the position feedback signals.
 56. The method of claim 55 whereinproviding further drive signals based at least in part on the positionfeedback signals includes providing further drive signals for moving afirst fluid body to a desired positioned before providing further drivesignals for moving a second fluid body.
 57. The method of claim 55wherein providing further drive signals based at least in part on theposition feedback signals includes adjusting a next set of drive signalsin response to the position feedback signals.
 58. The method of claim 55wherein providing further drive signals based at least in part on theposition feedback signals includes determining a next set of drivesignals based on a respective actual position and respective desiredposition of at least two fluid bodies with respect to a time.
 59. Themethod of claim 55, further comprising: determining a difference betweenan actual position and a desired position of the at least one fluidbody, and wherein providing further drive signals based at least in parton the position feedback signals includes compensating for thedetermined difference.
 60. The method of claim 55 wherein providingfurther drive signals based at least in part on the position feedbacksignals includes providing further drive signals to a first set of driveelectrodes along a first flow path to adjust a rate of movement of afirst fluid body along a first flow path and providing further drivesignals to a second set of drive electrodes along a second flow path toadjust a rate of movement of a second fluid body along a second flowpath.